The present invention generally relates to an improvement in closure apparatus used in drilling of oil wells and more particularly relates to an improvement to the automatic kelly valve closure apparatus disclosed in Taylor U.S. Pat. No. 3,331,385. Accordingly, the disclosure of U.S. Pat. No. 3,331,385 is specifically incorporated herein by reference.
Commonly used expressions for the present apparatus is a mud saver valve or automatic kelly valve. The automatic kelly valve, such as herein disclosed, is attached at the bottom of a drilling kelly and is a specialized tool with versatile characteristics. The valve is designed essentially to eliminate the loss of costly drilling fluids as is lost from the drilling kelly each time the kelly is connected to the drillpipe as the drillpipe is being added into the well by section during drilling operations. This automatic kelly valve automatically closes and retains the drilling fluid in the drilling kelly each time the kelly is disconnected from the drillpipe. The automatic kelly valve is spring loaded as a check valve and opens only when the pump pressure of the mud pumps becomes greater than the weight of the drilling fluid retained in the kelly. This prevents costly fluid loss and a hazardous muddy rig floor when the drilling crew are making connection or disconnection of the drillpipe.
At times, particularly when the drillpipe is being added into the well bore, an earth formation down within the well bore may have pressure exceeding the weight of the drilling fluid in the drill bore and the well is inclined to "kick" with pressure coming into the well from the well formation. This particular phenomena is aggravated with the sudden loss of fluid pressure as the mud pumps are stopped when a section of drillpipe is being added.
An advantage of the automatic kelly valve is that it has a tool port plug in the check valve body which may be removed when desired and' the oil well tool such as a point indicator or backoff shot device can be lowered through the kelly valve for performance down within or below the drillpipe. In the present invention a pressure gauge may be installed into a special test valve body provided below the automatic valve to test the pressure inside the drillpipe before the drillpipe connection is broken and also to sample the contents within the drillpipe as containing mud only or possibly gas along with the mud.
The presently known prior art consists of the following U.S. Pat. Nos.: Hart 403,751, Neighbors 946,684, Brown 1,462,099, Thomson 1,596,260, Nixon et al 1,674,055, Lemex 1,785,271, Baker et al 2,750,958, Callahan et al. 3,189,046, Brown 3,191,905, and Taylor 3,331,385 as previously mentioned.
The prior art is generally represented in FIG. 1 of the patent drawing. As shown, a closure apparatus or automatic kelly valve is connected between a drillpipe and a drilling kelly. The kelly is connected further into a swivel assembly including a swivel, bail and rotary hose. The assembly is further connected through piping to a mud pump (not shown).
Drilling fluids are pumped through the kelly, the closure apparatus and the drill string into a drill bit located at the bottom of the well bore. It is noted that hydraulic pressure is applied through the kelly and the drilling mud acts on the closure member to move the valve out of its valve seat. Pressure in the drill pipe operates to close the closure member off until such time as pressure within the kelly is sufficient to overcome the check valve spring in the closure.
When the drillpipe string is disconnected from the closure apparatus for any purpose, the mud pumping apparatus is shut off. The resilient spring of the valve in the closure comes into contact to seal the passage means through the kelly and the closing of the apparatus maintains a standing column of drilling fluid in the kelly above the closure apparatus. The retention of the drilling fluid in the kelly reduces waste of expensive drilling fluids and, even more especially, reduces the dangers inherent with a slippery and wet drilling platform to the drilling crew.
As will occasionally happen without forewarning, the drill may penetrate a reservoir under high pressure and gas and oil or a mixture of both, will tend to overcome the present pressure of column of drilling fluids standing in the drillpipe string. On such an occurrence, the reservoir pressure tends to force the drilling fluids back through the closure apparatus and through the kelly into the mud pumping apparatus. The closure apparatus operates to hold the drilling muds under any blowout pressure in the drillpipe string. The higher pressure acting on the closure valve urges the valve more firmly into contact with its seat.